Generator with blocking oscillator controls



May 25, 1965 J. l. MOSS ETAL GENERATOR WITH BLOCKING OSCILLATOR CONTROLS 5 1 a m i mw% m a f r m u 1 m nm N ay 1 IT Q Q w m m s w m v y 1965 J. 1. Moss ETAL 3,185,939

GENERATOR WITH BLOCKING OSCILLATOR CONTROLS Original Filed Sept. 12, 1958 2 Sheets-Sheet 2 *f a) L 2 a J: 1L

111/12 rzl ars 772/1111: fildss tl/l'la'arfiffimwrzer' United States Patent 3,185,939 GENERATOR WITH BLOCKING OSCILLATQR CONTROLS John I. Moss, Slrokie, 11]., and William J. Browner, San

Leandro, Caiifi, assignors to Relax-Acizor, Inc., a corporation of California Original application Sept. 12, 1958, Ser. No. 760,635, new Patent No. 3,108,597, dated (st. 29, 1963. Divided and this application May 6, 1963, Ser. No. 278,268

4 Claims. (Cl. 331-552) This invention relates to an electronic apparatus for generating electrical signals particularly designed for stimulating muscle activity.

This application is a division of Moss et al. application Serial No. 760,635, filed September 12, 1958, no Patent No. 3,108,597. I ""It is well-known that certain types of electrical impulses may beutilized for stimulating muscle action to achieve and maintain muscle tone and to eliminate soft 'flabby body tissue. This invention relates to a novel circuit for producing an improved electrical signal which achieves these results safely and efficiently.

Another object is to provide an electronic muscle stimulator including an electronic timing oscillator, switch means having first and second conditions, actuated by the timing oscillator, a pulse generator connected with the switch means and having an operative and an inoperative condition responsive to the switch means, together with means connected with the pulse generator for utilizing the pulses in the stimulation of muscle fibres.

A further object is to provide such a stimulator in which a timing multivibrator actuates the switch means, a timing pulse oscillator actuates a pulse responsive relay having switch means associated therewith which are actuated between a first condition and a second condition on successive pulses of the timing oscillator.

Further objects and advantages will become apparent from the following detailed description taken in connec tion with the accompanying drawings in which:

FIGURE 1 is a schematic diagram of an embodiment of the invention;

FIGURE 2 is a series of voltage wave forms taken as indicated in FIGURE 1, illustrating the operation of the circuit; and

FIGURE 3 is a modification of a portion of the circuit of FIGURE 1.

While this invention is susceptible of embodiments in many dilterent forms, there are shown in the drawings and will herein be described in detail a preferred embodiment of the invention and a modification thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and'is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

, Muscle stimulators of the general character disclosed herein are gaining increasingly wide acceptance for home use. The signals generated not only stimulate and exer cise the muscles improving tone and reducing fiab, but also have a relaxing effect on the user, reducing tension from worry, overwork and the like. One problem With previous apparatus is that it includes electronic circuits energized from a 110 volt standard service circuit and incorporates high voltage electronic tubes. The pads, or devices which are applied to the body to transmit the generated pulses to the muscles, must be moistened to improve the contact conductivity with the body, and while such apparatus is perfectly safe, a great deal of consumer resistance is encountered as a result of the fear of electrical shock. The novel system disclosed herein, utilizing transistor circuitry operating at a relatively low volt- Patented May 25, 1965 ice e, not only produces an improved muscle stimulating pulse, but also allays the fears of technically uneducated users regarding the safety of the device.

Turning now to FIGURE 1 of the drawings, the schematic there shown includes a transistor timing oscillator 10 which actuates a transistor switch 11. The switch in turn controls operation of transistor blocking oscillator 12, the output of which is coupled through output transistor 13 to a plurality of load circuits 14. The pulses appearing in load circuits 14 may be applied to the appropriate muscle actuating points of the user, as through a pad 15 equipped with strap 15a for securing the pad to the body. Various types of applicator padsot ditterent sizes and shapes may be used in stimulating different muscles. 1

The circuit of FIGURE 1, and its operation, will now be described in some detail, and values and type designations will be given for many of the circuit elements. It is to be understoodthat these specific figures are given primarily for the purpose of disclosing an operative embodiment of the invention, and the values are not to be considered critical. Many changes and modifications will readily be apparent to those skilled in the art.

The circuit is energized from a suitable source, as 24 volts DC. with the indicated polarity, connected to terminals 20 and 21, the power circuit being provided with an on-ofl switch 22. Multivibrator 10 includes a pair of lPNP transistors 23 and 24, each a 2N381, and each having its emitter electrode connected with power lead 21. The collectors of the transistors are returned, through resistors 25 and 26, each 5600 ohms, to power lead 27, which is connected through dropping resistor 28, 5600 ohms, with power lead 20. The base electrodes of the two transistors are connected to power lead 27 through resistors 29 and 30, each 180,000 ohms. The collector of transistor 23 is connected with the base of transistor 24 through coupling capacitor 31, 3 i. (microfarad), and the collector of transistor 24 is connected with the base of transistor 23 by capacitor 32, also 3 [.Lf.

The output signal of multivibrator '10 is illustrated in FIGURE 2A and comprises an essentially square wave pulse having a period t of the order of one and one-half seconds. This wave form is taken across transistor 24, as indicated in FIGURE 1. The square wave timing pulse is coupled from multivibrator 10 through dropping resistor 35 to the base of PNP switching transistor 36, a 2N381, appearing at the base in reduced amplitude (FIGURE 23). The emitter of switch transistor 36 is connected to the juncture of resistors 37, 560 ohms, and 38, 6800 ohms, forming a voltage divider between power leads 21 and 20. The blocking oscillator 12 is connected between the collector electrode of switch transistor 36 and power lead 20, transistor 36 serving to turn the energizing power for the blocking oscillator on and oil, in accordance with the timing pulses from multivibrator 10.

. Blocking oscillator 12 comprises a PNP transistor 40, 2N381, having its emitter connected to the collector oi transistor 36, and its collector connected through the primary winding 41a of transformer 41, to power lead 20; A feedback winding 41!) has one terminal connected with the base electrode of transistor 40 and the other terminal connected with a feedback circuit including capacitor 42,

2 at, connected to the emitter electrode of transistor 40,

and a resistive network including resistor 43, 15,000 ohms, and potentiometer 44, 25,000 ohms, to power lead 20. A capacitor 45, 8 t, is connected between the emitter element of transistor 40 and power lead 20.

When switch transistor 36 is rendered conductive by the timing signal from multivibrator 10, blocking oscillator transistor 40 is essentially connectedbetween power leads 21 and 20 through resistor 37 and the collector impedance of the switching transistor. As transistor 4h begins to conduct, the change in current in primary winding 41a induces a current in winding 41]) charging capacitor 42, applying a negative voltage to the emitter of the transistor. This cuts the transistor otr" providing a pulse type oscillation. The charge on capacitor 42. drains off through resistors 43 and 44-, whereupon the operation repeats. Resistor 46, 1000 ohms, shunts primary winding 41a, damping the oscillation and preventing a reverse potential from being applied to transistor 40.

The frequency or repetition rate of the pulses of the blocking oscillator is determined by the setting of variable resistor 44, and with the values of circuit components given above, a range of the order of 150 to 150 cycles per second is possible.

The power circuit for blocking oscillator transistor lt includes capacitor 45, connected in series with the collector impedance of the switch transistor 36 and resistor 37, and shunting the oscillator. When the switch is closed, i.e. when transistor 36 begins to conduct, capacitor 45 tends to charge along an exponential curve, the slope of which is determined by the relative values of the capacitor and the impedance of the charging circuit. The time constant of the charging circuit should be large with respect to the period of the blocking oscillator. This charging curve is illustrated in the left-hand portion of FIGURE 2C, from which it will be noted that the operating voltage for the blocking oscillator builds up gradually. Similarly, when transistor 36 is cut off, opening the switch, capacitor 45 tends to discharge along an exponential curve. As a result, the amplitude of the oscillations of blocking oscillator 40 increase gradually at the start of the operative period of the oscillator and decrease gradually at the termination thereof. This is illustrated by the wave form of FIGURE 2D, taken across output Winding 410 of transformer 41. FIGURE 2D shows, on an expanded time base t the wave form of one cycle of operation of the blocking oscillator.

In operation, the blocking oscillator has a duty cycle of about 50%, providing the desired pulsed output for approximately three-quarters of a second, and no output (a rest period) for three-quarters of a second. The gradual increase in the amplitude of the pulses upon initiation of the active portion of the cycle, and the gradual decrease on termination is extremely eflfective in conditioning the user to the stimulation. Where the signals start and stop abruptly, some users develop a fear of the impending stimulation and the desirable relaxing etfect is not achieved.

The output from the blocking oscillator is coupled to the base element of transistor 48, 2N301, in output circuit 13. The emitter of transistor 48 is connected to power lead 21 and the collector is connected through the primary winding 49a of output transformer 49, with power lead 20. The pulses (wave form 2D) applied to output transistor 48 act as switching signals, turning the transistor on or oif. The voltage wave form across primary winding 49a is essentially that of the signal applied to the base of output transistor 48. A portion t of waveform D is illustrated in FIGURE 2E, showing the pulse portion of the wave on a greatly expanded time base.

A plurality of secondary load windings, here four, are provided on transformer 49, and are each designated 4%. Connected with each secondary winding is a phasereversing, amplitude-varying resistive network made up of two variable resistors 52 and 53, which are cross connected with the terminals of the secondary winding. The movable taps of the two resistors are connected through a suitable cable 54 with pad 15.

The circuit of output transistor 43 is such that the transistor is saturated by the pulses from the blocking oscillator. Where the impedance in the collector or load circuit is large, i.e. no load on the system, the amount of current passed on each pulse depends primarily on this impedance. The collector to emitter voltage drops to a fraction of a volt and the voltage across the primary winding 4% of the output transformer is substantially the same as the supply voltage between leads 21 and 20. However, as the currents drawn by the loads connected to output windings 4% increase, the current in the output transistor circuit is limited by saturation of the transistor. With a condition which may be considered as normal operation, all four outputs set at about seven-eights of their maximum output potential, transistor 48 operates at seventy to eighty percent of saturation, and has a low alternating current impedance until saturation is reached. The output or load windings 49b of transformer 49 are tightly coupled with primary winding 49a. Thus, there is very little loss of power in the output circuit, and when the setting of the output circuit is varied, changing the load on the system, the voltage applied to the other loads is not effected substantially, as the current drawn through the primary winding depends upon the load impedance. This provides a high degreeof stability in operation so that a change in the condition of one output circuit does not require re-adjustment of the others.

An indicator lamp 55 is connected across one of the output windings 4%, through a resistor 56. This lamp not only provides an indication of output when the circuit is operating, but also serves to give notice to the operator when the power supply battery voltage is low, as the lamp will not light. In a typical circuit, the lamp may be a General Electric type 344, with resistor 56, 100 ohms.

A modified form of a portion of the invention is illustrated in FIGURE 3. Here, a transistor 60, 2N38l, is connected in a blocking oscillator circuit, by means of a feedback transformer 61 having a primary winding 61a in the collector circuit and secondary winding 61b in the circuit of the base. Connected in series with primary winding 61a is a pulse actuated relay 62 having associated therewith a switch 62a. This relay is so constructed that when a pulse of current is applied thereto the movable switch member 62a is transferred from contact 6212 to contact 62c. With the next pulse applied to relay 62, the position of the switch is reversed. Relays of this type may be obtained from many relay manufacturers. as Comar Electric Co., Chicago, Illinois.

When transistor 6% begins to conduct, at the start of a cycle of operation, the current flowing through winding 51a induces a current in winding 61b charging capacitors 63 and 6 cutting the transistor oiT. This charge then drains from capacitors 63 and 64- through resistors 65 and 66, the time constant of the circuit determining the frequency of operation of the blocking oscillator. Diode 6'7 prevents the application of reverse potentials to transistor 6d. The successive pulses applied to relay 62 cause actuation of movable contact 62a as described above.

Switch 62a, associated with relay 62, may be used in place of transistor 36 in the circuit of FIGURE 1, to effect control of the operation of pulse generating oscillator dtl.

We claim:

1. In an electronic muscle stimulator, means for generating electrical signals for muscle stimulation, comprising: a source of operating potential; a timing pulse generating transistor blocking oscillator having collector, emitter and base elements; a feedback transformer having a primary winding connected in the emitter-collector circuit of said transistor, across said source of operating potential, said transformer having a secondary Winding connected with said base; a reactance network connected between said secondary Winding and said source; a pulse responsive relay having an operating coil connected in series with said transformer primary in the emitter collector circuit of the transistor blocking oscillator and having switch means with a first and second condition, said switch means being periodically actuated from one condition to the other by successive pulses of said timing oscillator; a diode connected in parallel with the series combination of: said primary winding and relay coil and poled to conduct current flowing in a direction opposite the flow of current through said transistor to dissipate transient voltages developed in said transformer and relay coil; and a muscle stimulating signal generator connected with said switch means and having an operative and an inoperative condition, dependent on the condition of said switch means.

2. The electronic muscle stimulator signal generator of claim 1 wherein a variable resistance bias circuit is connected between said base and said source of operating potential.

3. In an electronic muscle stimulator, means for generating electrical signals for muscle stimulation, comprising: a single source of low operating potential; a timing pulse generating transistor blocking oscillator having collector, emitter and base elements; a feedback transformer having a primary winding connected in the emitter-collector circuit of said transistor, across said source of operating potential, said transformer having a secondary winding connected with said base; a pulse responsive relay having an operating coil connected in series with said transformer primary in the collector circuit of the transistor blocking oscillator and having switch means with a closed and open condition, said switch means being periodically actuated from one condition to the other by successive pulses of said timing oscillator; a diode connected in parallel with the series combination of said primary Winding and relay coil and poled to conduct current flowing in a direction opposite the flow of current through said transistor to dissipate transient voltages developed in said transformer and relay coil; a variable resistance bias circuit connected between said secondary winding and said source of low operating potential; a capacitance network connected between said emitter and the connection of said bias circuit and secondary winding; and a blocking oscillator power circuit connected with said switch means and having an operative and an 6 inoperative condition, dependent on the condition of said switch means.

4. In an electronic muscle stimulator, means for generating electrical signals for muscle stimulation, comprising: a single source of low operating potential; a timing pulse generating transistor blocking oscillator having collector, emitter and base elements; a feedback transformer having a primary winding connected to the collector of said transistor, said transformer having a secondary winding connected with said base; a pulse responsive relay having an operating coil connected in series with said transformer primary in the collector circuit of the transistor blocking oscillator and having switch means with a closed and open condition, said switch means being periodically actuated from one condition to the other by successive pulses of said timing oscillator; a diode connected in parallel with the series combination of said primary winding and relay coil and poled to conduct current flowing in a direction opposite the flow of current through said transistor to dissipate transient voltages developed in said transformer and relay coil; means connecting said source between said pulse responsive relay and said emitter; a variable resistance network connected between said sec ondary winding and said pulse responsive relay; a reactance network connected between said secondary winding and said emitter; and a muscle stimulating signal generator connected with said switch means and having an operative and an inoperative condition, dependent on the condition of said switch means.

References Cited by the Examiner UNITED STATES PATENTS 2,454,845 11/48 Sherman et al 331-185 2,745,012 5/56 Felker 331-112 2,981,898 4/61 St. John 331112 ROY LAKE, Primary Examiner.

JOHN KOMINSKI, Examiner. 

1. IN AN ELECTRONIC MUSCLE STIMULATOR, MEANS FOR GENERATING ELECTRICAL SIGNALS FOR MUSCLE STIMULATION, COMPRISING: A SOURCE OF OPERATING POTENTIAL; A TIMING PULSE GENERATING TRANSISTOR BLOCKING OSCILLATOR HAVING COLLECTOR, EMITTER AND BASE ELEMENTS; A FEEDBACK TRANSFORMER HAVING A PRIMARY WINDING CONNECTED IN THE EMITTER-COLLECTOR CIRCUIT OF SAID TRANSISTOR, ACROSS SAID SOURCE OF OPERATING POTENTIAL, SAID TRANSFORMER HAVING A SECONDARY WINDING CONNECTED WITH SAID BASE; A REACTANCE NETWORK CONNECTED BETWEEN SAID SECONDARY WINDING AND SAID SOURE; A PULSE RESPONSIVE RELAY HAVING AN OPERATING COIL CONNECTED IN SERIES WITH SAID TRANSFORMER PRIMARY IN THE EMITTER COLLECTOR CIRCUIT OF THE TRANSISTOR BLOCKING OSCILLATOR AND HAVING SWITCH MEANS WITH A FIRST AND SECOND CONDITION, SAID SWITCH MEANS BEING PERIODICALLY ACTUATED FROM ONE CONDITION TO THE OTHER BY SUCCESSIVE PULSE OF SAID TIMING OSCILLATOR; A DIODE CONNECTED IN PARALLEL WITH THE SERIES COMBINATION OF SAID PRIMARY WINDING AND RELAY COIL AND POLED TO CONDUCT CURRENT FLOWING IN A DIRECTION OPPOSITE THE FLOW CURRENT THROUGH SAID TRANSISTOR TO DISSIPATE TRANSIENT VOLTAGES DEVELOPED IN SAID TRANSFORMER AND RELAY COIL; AND A MUSCLE STIMULATING SIGNAL GENERATOR CONNECTED WITH SAID SWITCH MEANS AND HAVING AN OPERATIVE AND AN INOPERATIVE CONDITION, DEPENDENT ON THE CONDITION OF SAID SWITCH MEANS. 